[clang] [clang-cl]: Add /std:c++23preview and update _MSVC_LANG for C++23 (PR #112378)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

Question for @StephanTLavavej and @CaseyCarter -- are there plans to do something similar for C23 as done for C++23? (Anything else we need to do on our end?)

https://github.com/llvm/llvm-project/pull/112378